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An automatic identification system and method are provided which employ a
machine readable multiple layer label. The label has a plurality of
machine readable marking layers stacked one upon another. Each of the
marking layers encodes an identification symbol detectable using one or
more sensing technologies. The various marking layers may comprise the
same marking material or each marking layer may comprise a different
medium having characteristics detectable by a different sensing
technology. These sensing technologies include x-ray, radar, capacitance,
thermal, magnetic and ultrasonic. A complete symbol may be encoded within
each marking layer or a symbol may be segmented into fragments which are
then divided within a single marking layer or encoded across multiple
marking layers.

[0001] The invention was made by an employee of the United States
Government and may be manufactured and used by or for the Government for
governmental purposes without the payment of any royalties.

Claims

What is claimed is:

1. A machine readable multiple layer label to be read by a sensor, said
label comprising: a plurality of machine readable marking layers stacked
one upon another, each said marking layer encoding an identification
symbol detectable using the sensor.

4. The machine readable multiple layer label of claim 1, wherein the
symbols encoded by the marking layers are adapted to be detected using a
sensor providing non-optical detection of said symbols.

5. The machine readable multiple layer label of claim 1, wherein said
marking layers are comprised of the same sensing medium.

6. The machine readable multiple layer label of claim 5, wherein said
identification symbols of said marking layers are adapted to be detected
by a sensor comprising one of the group consisting of a x-ray sensor and
an ultrasonic sensor having tomographic capability.

7. The machine readable multiple layer label of claim 1, wherein each of
said marking layers comprise a different medium having characteristics
detectable by different respective sensors.

8. The machine readable multiple layer label of claim 7, wherein said
different sensors comprise at least two of the group consisting of x-ray,
radar, capacitance, thermal, magnetic, and ultrasonic.

10. The machine readable multiple layer label of claim 1 further
comprising at least one neutral layer disposed between two of said
plurality of marking layers.

11. The machine readable multiple layer label of claim 1 further
comprising a plurality of neutral layers, each of said neutral layers
separating two of said plurality of marking layers.

12. The machine readable multiple layer label of claim 1 wherein said
marking layers are stacked in an offset manner from one another.

13. A method for producing a multiple layer machine readable
identification label, said method comprising the steps of: (a) applying a
marking medium to a substrate layer to form a marking layer encoding a
machine readable identification symbol therein, the marking medium having
a detecting value that differs from that of the substrate layer; (b)
applying a neutral layer on the marking layer for spacing; (c) repeating
steps (a) and (b) until the desired number of marking layers are formed
and using the most recently applied neutral layer as the substrate layer
for the successive marking layer.

14. The method of claim 13 wherein the step of applying a marking medium
comprises a step of applying a marking medium to form an offset marking
layer.

15. The method of claim 13, wherein the step of applying a marking layer
comprises: applying a stencil having openings to the substrate layer; and
backfilling the openings with the marking medium.

16. The method of claim 13, wherein the step of applying a marking layer
comprises: applying a transfer tape to the substrate layer, the transfer
tape having an image composed of the marking medium formed thereon; and
inducing the image from the transfer tape to the substrate layer.

17. The method of claim 13, wherein the step of applying a marking layer
comprises: removing marking medium in selected area to form the machine
readable identification symbol.

18. The method of claim 13, wherein the step of applying a marking layer
comprises: forming a recess in the substrate layer; and backfilling the
recess with the marking media.

19. The method of claim 13, further comprising aligning images used to
form a segmented symbol.

20. The method of claim 13, further comprising: dividing a symbol into at
least two segments; and the step of applying marking medium to a
substrate layer includes a first step which encodes a first of the at
least two segments and a second step which encodes a second of the at
least two segments.

21. An automatic identification system, said system comprising: a
plurality of machine readable marking layers stacked one upon another,
each of said marking layers encoding a respective identification symbol,
and sensor means for detecting said respective identification symbol of
each of said marking layers.

22. The system of claim 21, wherein at least one of said identification
symbols comprises a two-dimensional symbol.

23. The system of claim 22, wherein said two-dimensional symbol comprises
a matrix forming an encoded array.

24. The system of claim 21, wherein said plurality of machine readable
marking layers are comprised of the same medium and said sensor means
comprises a sensor with tomographic capabilities for reading said
respective identification symbol from each of said marking layers.

25. The system of claim 21, wherein each of said marking layers comprises
a different medium having different characteristics; and said sensor
means comprises a plurality of different sensors, each of the sensors
detecting said symbol from a respective marking layer.

26. The system of claim 25, wherein said different sensors comprise two of
the group consisting of x-ray, radar, capacitance, thermal, magnetic, and
ultrasonic sensors.

27. The system of claim 24 wherein said sensor comprises one of the group
consisting of x-ray and ultrasonic sensors.

28. The system of claim 21, further comprising an opaque layer disposed
over said plurality of machine readable layers.

29. The system of claim 21, further comprising at least one neutral layer
disposed between two of said plurality of marking layers.

30. The system of claim 21, further comprising a plurality of neutral
layers, each said neutral layers separating any two of said plurality of
marking layers.

31. The system of claim 21, wherein identification symbols of at least two
of said marking layers comprises a first symbol fragment and a second
symbol fragment.

32. The system of claim 31 further comprising a processor for assembling
said first symbol fragment and said second symbol fragment after
detection thereof to thereby form a complete symbol.

33. A method of automatic identification, said method comprising the steps
of: applying a multiple marking layer label onto a component, each
marking layer encoding a respective identification symbol; and detecting
the respective identification symbol from each marking layer.

36. The method of claim 33, wherein each marking layer is comprised of the
same medium and said step of detecting the respective identification
symbol comprises the step of detecting each identification symbol using a
sensor which has tomographic capabilities for reading the identification
symbols from each said marking layer.

37. The method of claim 36 wherein the sensor comprises one of the group
consisting of x-ray and ultrasonic sensors.

38. The method of claim 33, wherein each marking layer comprises material
having different characteristics and the step of detecting the respective
identification symbol comprises detecting each identification symbol
using a plurality of different sensors, each sensor detecting the symbol
from a respective marking layer.

39. The method of claim 38, wherein the different sensors comprise two of
the group consisting of x-ray, radar, capacitance, thermal, magnetic, and
ultrasonic sensor.

40. The method of claim 33, further comprising applying an opaque layer
over the label.

41. The method of claim 33, wherein the label further comprises a neutral
layer disposed between two of the plurality of marking layers.

42. The method of claim 33, wherein the respective identification symbol
encoded in at least two marking layers comprise a respective symbol
fragment.

43. The method of claim 42, further comprising the step of assembling
detected symbol fragments thereby forming a complete symbol.

44. The method of claim 33, wherein the step of detecting the respective
identification symbol from each marking layer comprises the steps of:
collecting analog image signals emitted from the label; and converting
the analog image signals to a digital signal string using an analog to
digital converter.

45. The method of claim 44, further comprising the step of converting the
digital signal string into an ASCII data string.

46. The method of claim 45, further comprising the step of converting the
ASCII data string to a video signal that can be displayed on a video
monitor.

Description

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an identification method and
system which employ a multiple layer machine readable identification
label as well as to the label itself, and in particular, to an
identification method and system which employ a multiple layer machine
readable label having multiple marking layers each encoding a respective
identification symbol readable using one or a plurality of sensing
technologies to detect the symbol encoded therein.

[0004] 2. Background of the Invention

[0005] Private industries and government agencies such as automotive,
communication, distribution, manufacturing, medical/dental, nuclear,
pharmaceutical, printing/publishing, security, aerospace/aviation, and
defense have a need to apply markings (e.g., labels) to products for
esthetic and security reasons.

[0006] Conventional labels use single layer identification symbols such as
a UPC barcodes (one-dimensional symbols) and more recently
two-dimensional symbols (e.g. two-dimensional symbols named by the
automated identification and data collection (AIDC) industry).
Two-dimensional symbols may be matrix or stacked barcodes that form an
encoded array. U.S. Pat. Nos. 4,939,354 and 5,053,609 to Priddy et al.
disclose a matrix code (Data Matrix Symbol) designed as a label to be
applied directly to products. This matrix code can store from one to 2335
alphanumeric characters in any language.

[0007] FIG. 1 illustrates the basic elements of a matrix symbol known in
the art. Although shown as a square, matrix symbols may be of any shape.
However, square and rectangular shapes are most commonly used in the
industry. The unshaded squares comprising the matrix shown in FIG. 1 each
represent a binary "0" and the shaded squares each represent a binary
"1". FIG. 2 illustrates an example of a data matrix symbol as it would
appear on a product to be marked.

[0008] In specialized circumstances, it is advantageous to have the label
be invisible (i.e., not viewable to the naked eye). Currently, this may
be accomplished using inks that when applied to a visible surface, are
invisible to the unaided eye. These inks are produced by adding special
materials to a carrier ink. Using an appropriate sensor, the marking can
be detected.

[0009] One disadvantage with current invisible ink materials is that these
materials degrade over time. For example, these materials are adversely
affected by sunlight.

[0010] A second disadvantage with current identification markings is that
they are adapted to be optically detected. Consequently, these markings
cannot be read if covered by an opaque layer such as paint. Further, only
a single layer identification symbol can be used as a label to identify a
product because only a single (i.e., top) layer is detectable.

BRIEF SUMMARY OF THE INVENTION

[0011] In accordance with the present invention, a method and system are
provided which use a multiple layer machine readable identification
label. The multiple layer label comprises a plurality of marking layers.
Each marking layer encodes a respective identification symbol. The
marking layers are stacked on top of one another. All of the
identification symbols are read from the various marking layers using
either a single or multiple sensors. Such sensors include, but are not
limited to, x-ray, radar, capacitance, thermal, magnetic, and ultrasonic
sensors.

[0012] The invention, in one form thereof, concerns a machine readable
multiple layer label to be read by a sensor. The label comprises a
plurality of machine readable marking layers stacked one upon another.
Each of the marking layers encodes an identification symbol detectable
using the sensor. In one specific further embodiment, all of the marking
layers are composed of the same medium. The various identification
symbols encoded in the marking layers are detected using a single sensor
which has tomographic capabilities for discriminating between the marking
layers, thereby reading the symbols encoded on the various marking
layers. In an alternative embodiment, the various marking layers are
composed of different medium each having characteristics detected by a
respective, different sensor or sensing technology.

[0013] The invention, in another form thereof, relates to a method of
forming a multiple layer machine readable identification label. The
method comprises applying a marking medium to a substrate layer to form a
marking layer encoding a machine readable identification symbol therein.
The marking medium has a detecting value that differs from the detecting
value of the substrate layer. A neutral layer is applied over the marking
layer for spacing. Additional marking layers and neutral layers are
applied alternately until the desired number of marking layers are
formed. The most recently applied neutral layer acts as the substrate
layer for the successive marking layer.

[0014] The invention, in yet another embodiment thereof, concerns an
automatic identification system comprising a plurality of machine
readable marking layers stacked one upon another. Each of the marking
layers encodes a respective identification symbol. A sensor detects the
respective identification symbol from each of the marking layers. In
alternative embodiments, the plurality of machine readable marking layers
may comprise the same or a different medium.

[0015] The invention, in still another embodiment thereof, relates to a
method of automatic identification comprising applying a multiple marking
layer label onto a component. Each marking layer encodes a respective
identification symbol. The respective identification symbol is detected
from each marking layer.

[0016] It is an object of the present invention to provide an improved
method and system of automatic identification using a multiple layer
machine readable identification label.

[0017] It is another object of the present invention to provide a machine
readable identification label encoding identification symbols that is not
optically detectable.

[0018] It is yet another object of the present invention to provide a
machine readable label encoding identification symbols which are
detectable when covered by a subsequent coating such as an opaque layer.

[0019] It is still another object of the present invention to provide a
method and system for reading the various identification symbols encoded
in the marking layers which comprise a multiple layer machine readable
identification label.

[0020] Further features and advantages of the present invention will be
set forth in, or apparent from, the detailed description of preferred
embodiments thereof which follows.

BRIEF DESCRIPTION OF THE DRAWING

[0021] FIG. 1 illustrates the basic elements of a conventional matrix
symbol in the prior art;

[0022] FIG. 2 illustrates the elements of a completed data matrix symbol
known in the art;

[0033] FIG. 13 illustratively depicts another tape medium for carrying
multiple image sensitive media according to the present invention; and

[0034] FIG. 14 illustratively depicts a system for automatic
identification.

DETAILED DESCRIPTION OF THE INVENTION

[0035] Referring now to FIG. 3(a), multiple layer machine readable label
30 is formed on substrate 32. Label 30 is formed of alternate marking
layers 34 and neutral layers 36. The marking layers 34 encode
identification symbols. As such, marking layers 34 are active layers with
respect to sensing devices that will be used to detect the identification
symbols formed therein. Optimally, marking layers 34 are of a constant
thickness. The marking layers 34 are formed of the same material, thus
making them sensitive to a single sensing technology.

[0036] The neutral marking layers 36 are inactive layers with respect to
the sensing devices. Optimally, the neutral layers 36 are of a constant
thickness. The neutral layers 36 provide a substrate for subsequent
marking layers to be formed thereon. In addition, the neutral layers 36
enhance accuracy and efficiency of a sensing device with tomographic
capability.

[0037] The substrate surface upon which multiple layer label 30 is formed
may comprise the surface of a part or component to be marked.
Alternatively, a complete multiple layer label 30 may be first formed on
substrate 32 which is then bonded to the surface of part 38 (FIG. 3(b)).
In an alternate form, rather than being formed on the surface of a
substrate, multiple layer label 30 may be formed within a recess 33 of
the surface of a part 38 (FIG. 3(c)).

[0038] Referring now to FIG. 3(d), in another embodiment, multiple layer
label 31 comprises a plurality of marking layers 35, 37, each composed of
a different material. As such, marking layers 35, 37 have different
characteristics, and thus sensitive to a different sensing technology.
For example, marking layer 35 may comprises a magnetic detectable layer
and marking layer 37 may comprise a x-ray detectable layer.

[0040] Multiple layer label 50 represents an alternate offset design (FIG.
5). Each subsequent layer, both marking layer and neutral layer, is
formed on a previous layer at an offset exposing both edges of the
previous layer below. For example, marking layer 54 is formed on neutral
layer 56 such that the edges 58a, 58b are exposed. Similarly, neutral
layer 56 is formed on marking layer 55 such that edges 59a, 59b of
marking layer 55 are exposed.

[0041] Referring now to FIG. 6, multiple layer identification label 60
represents yet another multiple layer label having offset layers. Shown
as a top view, each subsequent layer is staggered relative to a layer
below such that the edges are exposed. For example, marking layer 64 is
formed on neutral layer 66 exposing edges 68 of neutral layer 66.
Similarly, neutral layer 66 is formed on marking layer 65 exposing edges
69.

[0042] Exposing the edges of the various layers comprising the multiple
layer identification label enhances tomographic efficiency. A sensor with
tomographic capabilities can more easily differentiate the various
marking layers comprising the multiple layer label with offset layers as
the resulting staggered exposed edges provides enhanced delineation
between the various layers comprising the multiple layer label.

[0043] Marking layers may be formed using any of a number of methods known
in the art. One such method is additive marking depicted in FIG. 7.
Marking medium 74 is applied to a layer of media of contrasting
emissivity such as substrate 72. The marking medium 74 is deposited such
that the layer formed thereby encodes an identification symbol to later
be detected using one or more sensing technologies.

[0044] Substrate 72 may be the surface of a product or part to be labeled
or may be a coating applied to the surface of a part. Any of a number of
methods known in the art may be used to apply marking medium 74 so long
as the methods do not adversely affect the properties or characteristics
of marking medium 74.

[0045] Further, as is apparent to one of ordinary skill in the art, an
appropriate marking method is selected based on the composition of
substrate 72, marking medium 74 and detection method to read an
identification symbol encoded therein. These methods include but are not
limited to the use of ink jet, laser bonding, silkscreen, stencil, and
thin film deposition.

[0046] Referring now to FIG. 8, marking 84 is produced by the technique of
direct marking, also known as, intrusive marking. Direct marking forms a
mark 84 by altering substrate surface 82 by abrading, cutting, burning,
vaporization, or other similar destructive method to produce an area of
contrasting characteristics or a recess that is subsequently back filled
with a media of contrasting characteristics. Included in this method are
dot peening, electrochemical etching, engraving, annealing, laser
etching, laser induced surface improvement (LISI), and milling.

[0047] Referring now to FIG. 9, marking medium 94 is produced by
subtractive marking through a process used to apply a layer of marking
medium that is subsequently removed in a selected area to expose a
surface of substrate 92. Substrate 92 has a contrasting emissivity from
that of marking medium 94. The technique of applying marking medium 94 to
substrate 92 includes dipping, barrier and chemical conversion coating,
planting and electro-planting, and vacuum controlled-atmosphere coating
and surface modification processing. Portion 98 is selectively removed
from deposited marking medium 94, for example, by a direct marking device
known in the art, thereby encoding an identification symbol in marking
layer 94.

[0048] The marking methods described with reference to FIGS. 7, 8 and 9
may be used on various metallic material substrates which include
aluminum, copper and its alloys, nickel and its alloys, heat and
corrosion resistant steels, tool steel, reactive and refractive metals,
coated, plated and/or special condition metals, and non-metals such as
polymetric materials, polymetric laminates, rubber, glass, and ceramics.

[0049] The neutral layers 36 may be applied in a similar manner as the
marking layer 34 or may be an inherent part of the component (e.g., part
or object) to be marked. For example, layers of a printed circuit board
could be marked (i.e., a marking layer deposited or formed thereon)
followed by multiple coats of paint or other protective layer applied
over the entire printed circuit board including the symbol marking layer
thereby forming a neutral layer. A subsequent symbol marking layer may
then be formed on top of the previously laid multiple coats of paints or
other protective coating prior to a subsequent multi-coating layer of
paint or protective layer.

[0050] Referring now to FIGS. 10(a)-10(c), symbol 100 may be segmented in
any of a number of logically divided patterns as indicated by broken
lines producing symbol fragments such as symbol fragments 102, 104, 106
(FIG. 10(a)); 108, 110, 112, 114 (FIG. 10(b)); and symbol fragments 116,
118, 120 and 122 (FIG. 10(c)). The various symbol fragments which
comprise symbol 100 may be encoded, divided, yet within a single marking
layer, or may be encoded within different marking layers.

[0051] Symbols 100 that are segmented (i.e., fragmented) in a logical
divided pattern and placed at different locations at the same marking
layer or at different marking layers may be reconstructed using
algorithms that rejoin data cell locators found at the boundaries at the
symbol division. Data cell locators are designated cell groups that are
assigned by the segmenting algorithm. They are adjoining at the segment
boundaries and are involved in the encoded information in the symbol. The
segmenting algorithm selects cell groups along the boundaries that will
constitute a verifiable match when reconstructed. After the symbol is
segmented, the reconstruction algorithm remembers the pattern and seeks
to reunite the cell groups in the same positions in the array as when
they were assigned as cell locators.

[0052] Referring now to FIG. 11, in an alternate marking method, tape
medium 130 carries a single image sensitive medium 140 on the surface of
tape medium 130 that will be placed in contact with a substrate surface
to be marked. Tape medium 130 also carries neutral layer 150 on the same
tape surface as medium 140. Neutral layer 150 contains a substance that
does not interfere with the readability/detectability of the material of
sensitive medium 140.

[0053] A heat transfer method, such as laser scribing a computer generated
pattern, transfers an image from tape medium 130 onto a substrate to be
marked thereby forming a marking layer which encodes an identification
symbol.

[0054] To generate a multiple layer identification label using tape medium
130, tape medium 130 is indexed into position on a substrate layer at a
target position such that image sensitive medium 130 is over the target
position. A pattern of medium 140 is transferred from tape medium 130 to
the substrate, forming a marking layer encoding a first identification
symbol therein. Tape medium 130 is then indexed, positioning one of the
neutral layers 150 over the first symbol. A neutral layer is formed over
the first symbol by transferring neutral layer 150 from tape medium 130.

[0055] Tape medium 130 is then indexed such that another image medium 140
is over the previously transferred neutral layer. A second symbol is then
marked on the previously transferred neutral layer. This process is
repeated until a desired multiple layer label is complete. The various
layers may be applied to a starting substrate which comprises a part to
be labeled. Alternatively, a complete label may be formed first on a
substrate material which is later bonded to the part to be labeled.

[0056] The symbols encoded may include a complete symbol or fragments
thereof. For example, rather than encoding a complete symbol at each
marking layer, a symbol layer may be divided into fragments. These
fragments can then be encoded across multiple marking layers or spread
out (i.e. divided) over the same marking layer. The symbol fragments are
detected and reassembled through algorithms to form the completed symbol.

[0057] Referring to FIG. 12, tape media 230 carries multiple image
sensitive media 240 such as magnetic medium 242, x-ray medium 244, and
radar medium 246. The multiple image sensitive media 240 and neutral
layer 250 are applied to the surface of tape medium 230 which will come
in contact with a substrate to be marked. The transfer method by which
the various image sensitive media 240 and neutral layer 250 are
transferred from tape medium 230 to the substrate to be marked is the
same as the transfer method described above in reference to tape medium
130.

[0058] When forming a multiple layer identification label composed of
multiple layers of different medium encoding a respective identification
symbol, tape 230 is indexed into position on a substrate to be marked
with one of the image sensitive media 240 over the target position on the
substrate to be marked.

[0059] For example, a first symbol detectable by a magnetic detector, may
be produced by indexing magnetic medium 242 over the target area. A first
symbol is marked on the substrate by transferring a selected portion of
the magnetic medium 242 to the substrate. Tape 230 is then indexed such
that neutral layer 250 is over the first symbol marked. A neutral layer
is then transferred from neutral layer 250 to the previously transferred
first symbol.

[0060] Next, tape 230 is indexed such that one of the remaining sensitive
medium 240 is over the previously transferred neutral layer. For example,
x-ray medium 244 may be indexed into position over the previously laid
neutral layer and a second symbol transferred onto the previously
transferred neutral layer. This process is repeated until the necessary
number of layers are formed. Tape medium 230 may be used to transfer a
complete symbol or fragments thereof in different locations on a single
marking layer or across different marking layers.

[0061] Referring now to FIG. 13, tape medium 330 may be used to carry
multiple image sensitive media 340 such as magnetic medium 342, x-ray
medium 344, radar medium 346, and infrared medium 348 on the surface of
tape medium 330 which will come into contact with a substrate to be
marked. The transfer method by which image sensitive media 340 is
transferred to a substrate is the same as the method used with tape
medium 230. The various image sensitive media 340 are indexed into
position such that alternate image sensitive media 340 is transferred
forming an identifiable symbol to a substrate or previously deposited
neutral layer until a desired multiple layer label is formed.

[0062] FIG. 14 illustratively depicts a system 400 for automatic
identification of a multiple layer machine readable identification symbol
430. Multiple layer label 430 is applied to component 438 and covered
with opaque layer 440. Detector 450 has sensor 452 for detecting the
identification symbols encoded in the various layers which comprise label
430. In addition, detector 450 is connected to computer 460 which in turn
is connected to host computer 470.

[0063] Sensor 452 has tomographic capabilities thereby detecting the
various identification symbols encoded in the various layers which
comprise multiple layer label 430. If multiple layer label 430 is
composed of marking layers of the same medium, e.g. ultrasonic or x-ray
detectable media, sensor 452 may incorporate a single sensor technology
such as x-ray or ultrasonic (depending on the medium encoding the
identification symbol to be detected). Both x-ray and ultrasonic sensing
technologies have tomographic capabilities that permit detection of the
respective identification symbols encoded in multiple layers of the same
type of marking medium.

[0065] If multiple layer label 430 is composed of marking layers of
different medium having different characteristics which encode the
various identification symbols, detector 450 incorporates multiple
sensors, each incorporating a different sensing technology. Each of the
different sensors reads a respective identification symbol from one of
the marking layers which compose the multiple layer label 420. For
example, detector 450 may incorporate x-ray sensing technique to detect
the identification symbol from a marking layer sensitive (i.e., response)
to x-ray detection. Another marking layer sensitive to thermal can be
detected by a thermal detecting sensor that is incorporated into detector
450. The various sensors which may be incorporated into detector 450,
include but are not limited to, x-ray, radar, capacitance, thermal,
magnetic, and ultrasonic sensor.

[0066] Although the invention has been described above in relation to
preferred embodiments thereof, it will be understood by those skilled in
the art that variations and modifications can be effected in these
preferred embodiments without departing from the scope and spirit of the
invention.